How to use the DRYIT semi-continuous tray dryer
Practical Action
The Selected sound fruit from the above test was then peeled and stoned and the % of usable
flesh weighed.
Supplier A
Supplier B
Supplier C
% of usable flesh
Variety 1
40
42
39
40.3%
Variety 2
46
47
45
46.0%
Variety 3
52
50
53
51.6%
This shows that the usable flesh depends on the variety and not on the supplier.
Knowing the relative prices of the 3 varieties, from the 3 suppliers, will now allow the
processor to decide which is the most economic to use.
Supplier A
(price per 100 kg)
Wt usable flesh (kg)
Cost of usable flesh
Supplier B
(price per 100 kg)
Wt usable flesh (kg)
Cost of usable flesh
Supplier C
(price per 100 kg)
Wt usable flesh (kg)
Cost of usable flesh
Variety 1
$10
36
27 c / kg
$8
37.1
22 c / kg
$10
35.1
28c / kg
Variety 2
$10
42.3
24 c /kg
$10
43.2
23 c /kg
$8
40.9
19.5 c /kg
Variety 3
$15
44.7
34 c/kg
$12
46.4
25 c/kg
$14
41.3
33 c/kg
This example shows that the best choice would be Variety 2 from supplier C which is not
perhaps the obvious conclusion from the original raw data and demonstrates how some simple
trials can affect profits. If supplier B and variety 3 had been selected (as the best in Table 1
above) prepared pulp would cost $250/ton while the final choice only cost $195. Once again
however 'life is not so simple' .It might well be found that one variety after drying had a much
better colour or flavour. This again would affect the final choice with questions having to be
asked as to whether using this variety would win a market, or put the price up to an
uncompetitive level.
Product drying ratio
During the drying process moisture is removed from the food product, so the weight of final
dry product is always less than the original weight put into the dryer. The ratio between the
final dry weight and initial weight put into the dryer is called the Drying Ratio and depends
upon the initial moisture and final moisture contents.
Initial moisture content. Ideally this needs to be checked in a laboratory but books are
available that give typical levels of a wide range of commodities. In general, moisture levels
of fresh produce lie between 75 and 90%.
The final moisture content depends on the product in question. It must be low enough to
make sure that micro-organisms such as moulds cannot grow.
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